Certain 2-acyl-2-thiazolines

ABSTRACT

The fried, roast or baked flavor of foodstuffs is improved by adding 2-acyl-2-thiazolines.

United States Patent Copleret al. 1 July 18, 1972 [54] CERTAIN Z-ACYL-Z-THIAZOLINES [56] References Cited [72] inventors: Harald Copier, Velp; Christian Herman ()THERP B Theodoor Tonsbeek, Zevenaar, both of U UCATIONS Netherlands Kuhn et al., Chemical Abstracts, 49:7555- 6 1954). [73] Assignee: Lever Brothers Company, New York, Primary Examine, A]ex Maze] Assistant Examiner-R. J. Gallagher [22] Filed: Jan. 7, 1970 Attorney-Louis F. Kline, Jr., Melvin H. Kurtz and Edgar E.

Ruff [21] Appl. No.: 1,284

ABSTRACT [52] U.S. CI ..260/306.7, 99/140 m f i d was! or baked fla f f d t ff is improved b i y [51] Int. Cl. ..C07j 9 /24 adding 2-acyl-2-thiaz0lines, [58] Field of Search ..260/306.7

4 Claims, No Drawings CERTAIN Z-ACYL-Z-TIHAELINEQ The invention relates to food flavours.

It provides a process for imparting an improved flavor to foods, in which there is incorporated in the food alone or in combination with one or more other flavoring agents, a 2-acyl- Z-thiazoline selected from 2-acetyl and 2-propionyl-2- thiazolines and their S-methyl, ethyl and propyl derivatives.

Preferably, 2-acetyl-2-thiazoline is used, but, for instance, 2-acetyl-5-methyl-2-thiazoline, 2-acetyl-5-propyl-2-thiazoline and 2-propionyl-2-thiazoline are suitable, as are 2-acetyl-5- ethyl-2-thiazoline, 2-acetyl-5-isopropyl-Z-thiazoline, 2- propionyl-S-methyI-Z-thiazoline, 2-propionyl-5-ethyl-2- thiazoline, 2-propionyl-5-propyl-2-thiazoline and 2-propionyl- S-isopropyl-Z-thiazoline.

These compounds are new.

They improve the characteristic flavor of fried, roast or baked products, such as meat sauces, sauces made from stock cubes, cakes, cookies, bread, and so on.

Other flavoring agents that can be used in conjunction with the new compounds are for example:

a. amino acids, which can be obtained by any traditional process from vegetable or animal proteins such as gluten, casein, zein, soya protein, and so on;

b. peptides of the same origin, as well as peptides such as alanylalanine, alanylphenylalanine, alanylasparagine, carnosine and anserine;

c. nucleotides, such as adenosine, guanosine, inosine, xanthosine, uridine and cytidine -monophosphates, as well as their amides, deoxidized derivatives and salts;

d. monocarboxylic acids, such as saturated or unsaturated fatty acids, for example those with two-l 2 carbon atoms, and lactic acid, glycollic acid and B-hydroxybutyric acid, as well as dicarboxylic acids, such as succinic acid and glutaric acid;

e. pyrrolidone carboyxlic acid and its precursors;

f. natural sweeteners, such as monoand disaccharides, and artificial sweeteners, such as saccharin,

g. 4-hydroxy-5-methyl-2,3-dihydrofuran-3-one and 4- hydroxy-2,5-dimethyl-2,B-dihydrofuran-S-one;

h. products from the reaction of sulphur-containing amino acids or hydrogen sulphide with reducing sugars, ascorbic acid, the compounds mentioned under g. or lower aliphatic aldehydes or ketones;

i. volatile sulphur compounds, such as hydrogen sulphide, mercaptans, sulphides and disulphides, for example dimethyl sulphide and diallyl sulphide;

j. guanidines, such as creatine and creatinene;

k. salts, such as sodium chloride and monoand di-sodium ,and ammonium phosphates;

1. organic phosphates, such as amino acids containing phosphorus;

m. nitrogen compounds which have not been mentioned above, such as ammonia, amines, urea, indole and skatole;

n. 4- and S-alkanolides as well as the esters and salts of the corresponding hydroxy acids, such as 5decanolide, 5- dodecanolide, sodium S-hydroxydecanoate and the glycerides of S-hydroxy acids, such as the products from the reaction of S-alkanolides with glycerol;

0. aldehydes, such as ethanal, propanal, 4-heptenal, etc.;

p. ketones, such as methyl ketones with, for example, five-l 5 carbon atoms, and biacetyl;

q. 3-oxoalkanoates, such as glycerol esters;

r. tn'cholinic and ibotenic acid and their salts;

s. flavoring agents, such as o-aminoacetophenone, N- acetonylpyrrole, maltol, isomaltol, ethylmaltol, vanillin, ethylvanillin, cyclotene( 2-hydroxy-3-methyl-2-cyclopentenel one), ethone [l-(p-methoxy-phenyl)-l-pentene-S-one], coumarin, and ethoxymethylcoumarin;

t. alcohols, such as ethanol and octanol;

u. essences, such as butterscotch and nut essence;

v. colorants, such as turmeric and caramel;

w. thickeners, such as gelatin and starch;

x. emulsifiers, such as the monoglyoerides of diacetyltartaric acid.

The quantity of these additives is determined by the nature of the food and that of the other additives, such as herbs and spices, as well as by the nature of the flavor one wants to give.

The quantity of 2-acyl-2-thiazoline in the food when ready for consumption may vary between 0.01 and 5 mg/kg. The exact quantity to achieve a well-balanced flavor can be determined by tests in each individual case. The flavoring agent can be added to the food ready to be prepared. It can also be incorporated alone or in combination with other flavoring agents, in an edible diluent or carrier, which in one preferred embodiment is a constituent or a mixture of constituents of the food.

It is thus possible, for example, to dissolve the flavoring agent in the aqueous phase, such as the one which is prepared for the production of margarine, and use this aqueous phase afterwards for the production of the margarine to be used in preparing foods. It is also possible to incorporate the flavoring agents in the food by mixing them with flour, fat or water.

To facilitate easy measuring of such small quantities of 2- acyl-Z-thiazolines, they can be incorporated in an edible powder, in a higher content; of such an edible powder, containing preferably 0.1 to 10 mg/g of the flavoring agent, the appropriate amount can more easily be dosed in preparing the food than the flavoring agent itself.

Incorporation can be performed by mixing the amount of 2- acyl-2-thiazoline with the edible powder, which is blended with the components of the food.

It is also possible to mix a solution of the flavoring agent intimately with the edible power and, if necessary, to eliminate the solvent afterwards.

A powder containing the flavoring agent, which can be easily measured, is obtained by dissolving the required quantity of the flavoring agent in a concentrated aqueous solution of dextrine-maltose and subsequently eliminating the water from this solution, preferably by lyophilization or spray-drying.

It is advisable, according to the required application, to use 0.1 to 10 mg of flavoring agent per gram of edible powder, but it is also possible to use larger or smaller quantities.

To these powders, in particular to those with a dextrinemaltose basis, it is also possible to add other useful flavoring agents, as for example 4- and 5alkanolides, 4-hydroxy-5- methyl-2,3-dihydrofuran-3-one, 4-hydroxy-2,5-dimethyl-2,3- dihydrofuran-3-one, methyl ketones and other of the substances mentioned above.

Another possibility is to incorporate the 2-acyl-2-thiazolines with solid or liquid flavoring compositions which can be added as condiments to the foods when consumed to give them a better flavor of fried or roast foods. The consumer can then add these flavoring compositions to a dish or a fried food either in the kitchen or at the table to adjust the flavor. These flavoring compositions can also include kno'wn substances, such as salt, mono-sodium glutamate, a protein hydrolysate and other substances mentioned in the above list.

It is possible to obtain the 2-acyl-2-thiazolines in various ways.

For example a l-amino-Z-alkanethiol of the general formula II, for example l-amino-2-ethanethiol, can be made to react with a 2,2-dialkoxy-alkane-nitrile of the'general formula III, the ketal (formula VI) obtained being hydrolyzed to give the required compound In these formulas, R is a methyl or ethyl group, R is a hydrogen atom or a C,C alkyl group and R and R represent alkyl radicals, whether difierent or not, which are preferably methyl or ethyl radicals. The hydrolysis is preferably carried out in concentrated sulphuric acid at C.

It is also possible, for example, to make the 1-amino-2-alkane-thiol (l1) react with a 2-alkoxy-2-alkenenitrile of the general formula IV, and then hydrolyze the enolether obtained (formula VII) to give the required compound In these formulas, R and R have the same signification as above, and R represents a hydrogen atom or a methyl group, thus numbering one carbon atom less than R.

Another possible route is coupling the 1-amino-2-alkanethiol (11) with a 2-hydroxyimino-alkanenitrile of the general formula V and hydrolyzing the oxime (VIII) of the flavoring agent with acid in which R and R have the same meaning as above.

EXAMPLES EXAMPLE 1 Under stirring, 50 g ammonium acetate, 24.15 g (0.3 mole) cysteamine, 28.6 g (0.2 mole) 2,2-diethoxypropanenitrile (prepared according to T. Cuvigny, Bull. Soc. Chim. France 1957, 665) and 200 ml absolute methanol were mixed under a nitrogen blanket at ambient temperature. Stirring was continued for 18 hours, and the reaction mixture was then kept for 6 hours at about 70 while a current of nitrogen was slowly passed through. After eliminating most of the solvent under a pressure of 20 mm Hg at 30, the residue was poured onto a mixture of a solution of 45 g potassium hydroxide in 400 ml water and 100 ml diethyl ether at 0. After thorough mixing, the ethereal layer was separated, and the aqueous layer extracted with 5 portions of 100 ml ether. The ethereal extracts were combined and dried with anhydrous sodium sulphate for one hour and subsequently with potassium hydroxide tablets for 3 hours. The ethereal solution was decolorized with active carbon and filtered using a Hyflo supercel filter aid; the sol vent was evaporated under diminished pressure. By vacuum distillation 34.6 g 2(1,1-diethoxy-ethyl)-2-thiazoline, bp. 93-93.5 at 1.5 mm Hg, N 1.4822, was obtained; yield 85 percent. The main absorption bands in the infrared range were at 1,620, 1,240, 1,170, 1,070 and 1,030 cm. The main peaks of the mass spectrum, classified according to decreasing intensity, were situated at rule 43, 61, 117, 89, 88, 130, 60, 59, 159, 158; the parent peak at m/e 203 was not intense. The NMR spectrum (with tetramethylsilane as internal standard): large triplet for 84.27, quartet for 83.50, large triplet for 83.15, singlet for 81.48 and triplet for 81.17 ppm, attributed to the presence of CH at C-atom no. 4, CH of ethoxy groups, CH at C-atom no. 5, CH at the quaternary C-atom and CH, of the ethoxy groups respectively.

34 g 2-( 1,1-diethoxyethyl)-2-thiazo1ine was added dropwise to 136 ml 96 percent sulphuric acid, under stirring, the temperature being maintained at 0-5 by cooling; stirring was continued for 15 min afier the completed addition. The reaction product was carefully pouted into a mixture of 500 g sodium hydrogen carbonate, 1,500 g ice and 200 ml ether, after which another 1.5-2 1 iced water were added. It was then extracted with 5 portions of 200 ml dichloromethane; the combined extracts were filtered through dry cotton wool and dried with anhydrous sodium sulphate. The solvent was evaporated in vacuo. The residue yielded on vacuum destillation 19.7 g 2- acetyI-Z-thiazoline, colorless crystals, mp. 24.526 C, bp. 94 at 12 mm Hg, n,,"= 1.5294. Yield 91 percent. The main absorption bands in the infrared range were at 1,700, 1,595, 1,420, 1,360, 1,260, 1,248, 1,037, 995, 940, 910, 700, 610 and 550 cm. The main peaks of the mass spectrum are situated at m/e 129 (21), 101 (5), 87 (6), 60 (45), 59 (16), 58 (6), 45 (14), 44 (9), 43 (100), 42 (7.5) and 41 (7), the figures indicated in brackets representing the intensities in relation to the most intense peak, i.e. that for m/e 43. The parent peak is situated at m/e 129. Ultraviolet spectrum maxima: in water at 304 nm (6 1300 cm lmmole); in pentane at 229 nm (e 1,400 cmlmmole). The NMR spectrum (with tetramethylsilane as internal standard): large triplet for 84.48, large triplet for 83.25, singulet for 82.44 ppm, attributed to the presence of CH at C-atom no. 4, CH at C-atom no. 5 and CH respectively. The threshold value for the flavor in an aqueous solution at 20 C. is 0.01 ppm.

EXAMPLE 2 In a similar way were prepared A. 2-propionyl-2-thiazoline, bp. 52 at 0.25 mm Hg; n 1.5297. Infrared absorption maxima at 2,980, 2,940, 2,880, 2,850, 1,700, 1,595, 1,460, 1,447, 1,408, 1,378, 1,385, 1,210, 1,078, 992, 880, 800, 700 and 600 cm". The ultraviolet absorption spectrum in pentane had a maximum at 300 n,,, (6 1650 cm /mmole). The main peaks of the mass spectrum are situated at m/e 143 (22), 115 (16), 88(5), 87 (13), 60 (28), 59 12), 58 (5), 57 (100) and 45 (9), the figures in brackets representing the intensities in relation to the most intensive peak at rule 57. The parent peak is at m/e 143. The NMR spectrum with tetramethylsilane as internal standard): triplet for 84.48, triplet for 83.28, quartet for 82.88 and triplet for 81.1 1 ppm, attributed to the presence of CH at C-atom no. 4, CH at C-atom no. 5, CH adjacent to the CO group, and CH respectively. B. 2-acetyl-5-methyl-2-thiazoline, bp. at 9.5 mm Hg; n 1.5128; ultraviolet maximum at 297 nm (e 1.665 cm lmmole); infrared absorption maxima at 2,965, 2,930, 2,870, 2,840, 1,704, 1,590, 1,450, 1,433, 1,420, 1,376, 1,359, 1,310, 1,250, 1,040, 935, 910, 615 and 568 cm". The NMR spectrum (with tetramethylsilane as internal standard): multiplets for 84.51 and 4.17, multiplet for 83,88, singulet for 82.50 and doublet for 81.33 ppm, attributed to the presence of CH; at Catom no. 4, CH at C-atom no. 5, CH adjacent to the CO group and CH substituted at C-atom no. 5 respectively.

The main peaks of the mass spectrum are situated at m/e 143 (45), 74 (60), 59(8), 45(6), 43 and 41 (22), the figures between brackets again representing the peak intensities relative to that of rule 43. The parent peak is at m/e 143. C. 2-acetyl-5-propyl-2-thiazoline, bp. 90 at 0.3 mm Hg; n 1.5029; ultraviolet maximum at 296 nm (e 1.690 cm /mmole); infrared absorption maxima at 2,960, 2,930, 2,870, 2,840, 1,700, 1,590, 1,463, 1,433, 1,416, 1,378, 1,358, 1,250, 1,038, 920, 615 and 578 cm". The NMR spectrum (with tetramethylsilane as internal standard): multiplets for 84.15 and 4.48, multiplet for 83.85, singulet for 82.43, multiplet for 81.11.9 and triplet for 80.95 ppm, attributed to CH at C- atom no. 4, CH at C-atom no. 5, CH;, adjacent to CO group, CH groups of propyl group, CH, of propyl group respectively. The main peaks ofthe mass spectrum are at m/e 171 (24), 128 (20), 102 (12), 89(6), 87 (16), 86 (32), 74(7), 73 (7), 72 (5), 70(6), 69 (20), 68 (15), 61 (13), 60 (25), 59 (15), 56

(7), 55 (20), 54(5), 47(7), 45 (11), 43 (100), 42 (11) and 41 (42), the figures between brackets again representing the relative intensities. The parent peak is at m/e 171.

In the same way 2-propionyl-5-methyl-2-thiazoline was prepared from Z-hydroxyimino-butanenitrile and 1-amino-2- propanethiol. B.p. 56-57 C. at 0.4 mm Hg; n 1.5072; ultraviolet absorption maximum in pentane at 297 nm 1420 cm /mmole); infrared absorption maxima at 2,970, 2,930, 1,700, 1,590, 1,450, 1,430, 1,405, 1,375, 1,358, 1,205, 1,078, 971, 929, 877, 800, 725 and 708 cm. The NMR spectrum (with tetramethylsilane as internal standard): multiplets at 64.52 and 4.18, multiplet at 8 3.83, quartet at 8 2.85, doublet at 6 1.32 and triplet at 6 1.10 p.p.m., attributed to CH at G atom No. 4, CH at C-atom No. 5, CH of propionyl group, Cl l of methyl group and CH of propionyl group, respectively. The main peaks ofthe mass spectrum are at m/e 157 (33), 129

(7), 102(5), 101 (12), 87(5), 74 (36), 72(7), 60 (8), 59 (10), 58(5), 57 (100), 56(5), 45 (10), 42 (12), 41 (35) and 39 14), the figures between brackets representing the intensities relative to the peak at rule 57. The parent peak is at m/e 157.

EXAMPLE 3 2-Hydroxyimino-butanenitrile was prepared by oxidation from 2-hydroxyamino-butanenitrile in a 56 percent yield according to Kissinger and Ungnade, J. Org. Chem 25, 1471 (1960); bp. 62 C. at 3.5 mm Hg, n 1.4532.

To 7.1 g (72.4 mmole) 2-hydroxyirnino-butanenitrile were subsequently added: 11.15 g (145 mmole) cysteamine, 70 ml methanol and 14.0 g anhydrous ammonium acetate. The mixture was allowed to stand under nitrogen for 24 hours, The methanol was evaporated under diminished pressure. The residue was poured onto 100 ml iced water. The resulting mixture was extracted with five portions of 50 ml diethyl ether each. The combined ethereal extracts were dried with anhydrous sodium sulphate, after which the ether was evaporated. The white solid residue (10.7 g) was recrystallized from dichloromethane at low temperature. The purified substance, 2-(1-hydroxyiminopropyl)-2-thiazoline, melted at l5ll52 C. Under stirring, a quantity of 9.70 g (61.3 mmole) 2-(1-hydroxyiminopropyl)-2-thiazoline was added in small portions to 150 ml 12N hydrochloric acid; it dissolved immediately. The solution was allowed to stand at ambient temperature; after 16 hours the solution was carefully poured into a mixture of 100 ml ice (partly melted), 50 m1 dichloromethane and 160 g potassium hydrogen carbonate. After separating the layers, the aqueous layer was extracted with four portions of 100 ml dichloromethane each. The extracts were combined with dichloromethane layer and dried with anhydrous sodium sulphate. After evaporating the solvent under diminished pressure, the residue was fractionated in vacuo, yielding 5.0 g of a colorless liquid, boiling at 52 C. at 0.25 mm Hg. Yield 57 percent n 1.5297. The 2-propionyl-2-thiazoline so prepared showed only one peak in a gaschromatograrn. The physical properties are equal to those represented in Example 2 A.

EXAMPLE 4 A composition which contains the flavoring agent and which is easier to measure was prepared as follows 0.175 g of 2-acetyl-2-thiazoline was dissolved in 500 ml of a 50 percent solution of dextrine-maltose in water; the whole was intimately mixed and the solution lyophilized. The powder obtained contained 0.7 mg of 2-acetyl-2-thiazole per gram.

Fur purposes of comparison, a reference powder without the flavoring agent was prepared by lyophilization of a 50 percent aqueous dextrine-maltose solution.

The powder containing the flavoring agent can, if necessary, be diluted by mixing it intimately with the reference powder. It is also possible to dissolve a smaller quantity of the flavoring agent or to use a larger amount of the dextrine-maltose solution to obtain more diluted powders. More concentrated powders can possibly also be prepared.

In the same way powders containing other flavoring agents according to the invention can be prepared.

EXAMPLE 5 A paprika meat sauce was prepared from the following ingredients Parts by weight fresh paprika, chopped powdered paprika 12 fresh onion, chopped tomato concentrate 30 salt 15 p pp 1 powdered garlic 0.1 hardened fat 30 wheat flour 60 meat 250 dextrine-maltose powder containing the flavoring agent (0.16 rng/gasin Example 4) 0.5 water up to 1000 The meat was browned with the fat in a frying pan. The onion and the chopped paprika were added and lightly cooked. Then 200 parts by weight of water and the remainder of the ingredients, except for the wheat flour and the dextrinemaltose powder, were added and the whole was brought to the boil. The wheat flour and the dextrine-maltose powder were mixed with 200 parts by weight of water to thicken the sauce. Finally, the rest of the water was added.

A reference sauce was prepared in the same way while using unflavored dextrine-maltose powder.

In an organoleptic test carried out by a group of twelve tasters the sample containing the flavoring agent was preferred by ten respondents for its savor and its more aromatic smell.

EXAMPLE 6 A tomato meat sauce was prepared from the following ingredients:

Parts by weight Tomato concentrate onion, chopped 60 beef fat 50 beef meat 200 wheat flour 30 salt 1 2 monosodium glutamate 2 herbs and spices mixture 5 water 490 aqueous solution of 2-acetyl-S-methyl-2- thiazoline (0.38 mg/ml) 2 The meat was browned with the fat and the onions added and fried for a few minutes; 400 ml water and the other ingredients, except the flour and the aqueous solution of the flavoring agent, were added. Under stirring, the mixture was heated to boiling after which the sauce was thickened by slowly adding a mixture of the flour and 90 ml water. Boiling was continued for 5 minutes. Then the aqueous solution of the flavoring agent was added.

A reference sauce was prepared in the same way whereby instead of the aqueous solution of the flavoring agent, 2 ml water was added.

Both sauces were tested organoleptically by a panel of 21 tasters, of which 17 preferred the flavored sauce for its fresher taste and smell, which were more like fried meat.

EXAMPLE 7 Stock'cubes were prepared in the traditional way from the following ingredients Pepper 0.02 Powdered bay leaves 0.02 Powdered clove 0.02 Salt 8 Powdered protein hydrolysate 4 Powdered meat extract 2 Powdered tomato 6 Powdered dextrine-maltose flavored (0.7 myg) as in Example 4 0.4

A broth was prepared by diluting 43.8 g of these cubes in l l of boiling water. A reference broth was prepared in the same way, but using unflavored dextrine-maltose powder. The sample containing the 2-acetyl-2-thiazoline was markedly preferred to the reference broth for its smell and its richer flavor.

EXAMPLE 8 Stock cubes were prepared in the traditional way by mixing the following ingredients, and pressing cubes of 23 g each Parts by weight Monosodium glutamate 300 beef fat 500 herbs and spices mixture 50 salt 700 powdered protein hydrolysate 500 powdered meat extract 200 dextrine-maltose flavored with 2-acetyl-5- propyl-Z-thiazoline (4 gs) as in Example 4 50 By dissolving one cube in l l boiling water, a broth of a more tasty ans richer flavor was obtained as compared with a sauce prepared in a similar way using non-flavored dextn'ne maltose.

Instead of using flavored dextrine-maltose a flavored sauce can be prepared by adding 1 ml of an aqueous solution of 2 mg flavoring agent in 1 ml water to l l of non-flavored sauce.

EXAMPLE 9 A cake was repared from the following ingredients g Margarine 150 lmpalpable sugar [75 Self-raising flour 200 3 whole hen eggs 150 Salt 1 Powdered dextrine-maltose flavoured (0.7

s g) as in Example 4 0.5

The margarine and the sugar were mixed intimately for minutes so as to form a homogeneous paste. The eggs were added one by one and mixed intimately for one minute after each addition. The self-raising flour and the other ingredients EXANIPLE 1O Shortcakes were prepared from the following ingredients Wheat flour 400 Sugar 200 Margarine 300 Aqueous solution of 2-propionyl-2-thiazoline 1 mg/ml) 5 The first three ingredients were well mixed in a Hobart mixer for 5 minutes. Then the aqueous solution of the flavoring agent was kneaded through the dough, after which the mixture was kneaded by hand for another 5 minutes.

The short cakes were prepared by baking at C. for 30 minutes. Reference short cakes were prepared in the same way whereby instead of the aqueous solution of the flavoring agent 5 ml water were added. The short cakes were organoleptically tested by a panel of 12 tasters, of which 8 preferred the flavored short cakes for their more tasty and well-baked flavor.

EXAMPLE 1 l A sprinkling powder was prepared in the traditional way from the following ingredients Parts by weight Monosodium glutamate 4 Salt 7 Powdered protein hydrolysate 4 Pepper 0.02 Powdered bay leaves 0.02 Powdered cloves 0.02 Powdered onion 1 Yeast extract 1.5 Powdered dextrine-maltose flavored (7 mg/g) as in Example 4 0.8

By adding this powder in the proportion of 200 mg per 0.5 l of already prepared meat sauce and by mixing the whole, a sauce with a richer and more marked flavor was obtained.

What is claimed is:

l. 2-Acetyl-S-methyLZ-thiazoline.

2. 2-Acetyl-5-propyl-2-thiazoline.

3. 2-Pr0pionyl-2-thiazoline.

4. 2-Propionyl-5-methyl-2-thiazoline. 

2. 2-Acetyl-5-propyl-2-thiazoline.
 3. 2-Propionyl-2-thiazoline.
 4. 2-Propionyl-5-methyl-2-thiazoline. 